Dino-killing asteroid had a ripple effect

摘要

The asteroid impact that slew the dinosaurs may have also indirectly sculpted the largest ripple marks ever found on Earth.A series of ridgelike structures more than three stories high and spaced nearly two Eiffel Towers apart appear to be buried about 1.5 kilometers beneath central Louisiana. The oversized features are megaripples shaped by a massive tsunami generated by the Chicxulub asteroid impact, researchers argue in the Sept. 15 Earth and Planetary Science Letters."It's just interesting that something that happened 66 million years ago could be so well preserved, buried 5,000 feet down in the sediments of Louisiana," says geologist Gary Kinsland of the University of Louisiana at Lafayette.Ripple marks are repeating sequences of ridges typically found on sandy beaches or stream bottoms and form as wind or water flows over and moves loose sediment. But ripple marks on the beach are often centimeters in height, while the structures found by Kinsland's team have an average height of 16 meters and are spaced about 600 meters apart.